Spraying apparatus



NOV. 14, 1944. w, HQUGHTON 2,362,634

SPRAYING APPARATUS Filed Aug. 20, 1942 66 //\/l/EN TU/Fi y 3;,

Patented Nov. 14, 1944 UNITED STATES PATENT OFFICE SPBAYING APPARATUSWilliam M. Heighten, Marblehead, Masa, assignor to United Shoe MachineryCorporation, Fiemington, hi. 1., a corporation of New Jersey ApplicationAugust, 1942, Serial No. 455 ,4155

4 Claims. (Cl. 299-140) This invention pertains to apparatus for applying a coating to articles and more especially to means for sprayingshoe parts with coatin material.

The apparatus illustrated herein for sprayins coating materialcomprises, in part, a conventional spray gun upon the barrel of which isplaced a heating coil for heating the coating material as it passesthrough the spray gun. Under normal conditions the spray gun is usedintermittently. That is, between each spraying operation there may be aconsiderable period of time and consequently it the same amount of heatis supplied to the spray gun when it is idle as is supplied to it whenit is in operation to liquefy the coating material during its passagethrough the spray gun the temperature will build up to such an extentthat during thesucceeding spraying operation the coating material may beoverheated and thus spoiled, or, the gun may be damaged.

It is an object of the present invention to provide means formaintaining the spraying apparatus at a substantially constantpredetermined temperature irrespective of whether it is in operation oris idle.

In the illustrated apparatus, coating material is forced through aheating chamber to a spray nozzle by a fluid under pressure and isheated during its passage through the chamber by heatin means associatedwith the chamber. A valve is provided for controlling the flow of thecoating material and, in accordance with a feature of the invention, thevalve is operable to cause the heating means to maintain a substantiallying coil is placed about the barrel of the spray gun to heat the coatingmaterial which is forced therethrough, as will appear hereinafter.

In shoe manufacturing, the application of the coating material to shoeparts is not a continuous operation. That is, after each part is coatedthere is an appreciable interval before the next part is coated.andbetween one rack of shoe parts and the next there may be aconsiderable period of time. During the intervals when the spray gun isnot being used and when no coating material is passing through it, thetemperature builds up and, consequently, when the next coating operationis performed the coating material may be overheated to such an extent asto spoil its properties as a covering agent. Furthermore, there is alsothe danger of overheating the spray gun itself. To prevent this, themotivating means for driving the coating material through the spray gunand a pressure-operated switch controlling the electric circuit forheating the spray gun are interconnected in a manner to maintain 1 thespray gun at a substantially uniform temuniform temperature in thechamber irrespective of whether the valve is open or closed.

The details of the apparatus will now be de scribed with reference tothe accompanying drawing, in which Fig. 1 shows the spray n. in section;

Fig. 2 shows an end elevation of the spray gun as seen from the rightside 0! Fig. 1;

Fig. 3 shows a diagrammatic view of the spray gun, the air conduitsconnected thereto, and the heating circuit; and 1 Fig. 4 shows thedetails of the pressure-operated switch.

Most coating materials are quite viscous at room temperature and,accordingly, when applied to articles by a spray gun, means must beprovided for heating the material before it reaches the spray gun orduring its passage through the spray gun to make it liquidenoushperature regardless of whether the coating material is or is not passingthrough it.

Referring to Fig. l, the spray gun G is shown as comprising a barrel illhaving a nozzle l2 at one end, interior passages It, It for deliveringair and It for delivering coating material to the nozzle, and a needlevalve It in the passage It for controlling the passage of the coatingmaterial through the nozzle. The needle valve ll passes through apacking gland 20 at the rear of the barrel l0 and has fixed thereto atits end a piston 22. A cylinder 24 closed at one end is threaded on therear end of the barrel and provides a chamber 26 for the piston 22. Acompression spring 28 is interposed between thepiston 22 and the closedend of the cylinder 24 to urge the needle valv toward a position toclose the fluid passage it near the nozzle l2. A passage 2. in the bodyof the spray gun permits access of air under pressure to the chamber 2|and thus to the front side of the piston 22, thereby providing means toopen the needle valve ll against the opposition of the compressionspring 2!. A part of the air which gains access to the chamber 2! passesthrough the passages is to the nozzle I! of the spray gun, therebyproviding means for atomizing the coating material delivered to thenozzle through the passage II. A nipple 32 (Fig. 2) is threaded into thebarrel ll of the spray gun and provides a connection between the barrel0! the spray gun and an air tobeatomised. Inthepresentapparatusaheat- 56conduit 34 (Fig. 3) by which'air under pressure ,cuit 62 by leads 64 and56.

is delivered through the passage 30 to the chamber 26. A second nipple36 provides a connection between the fluid passage I in the barrel ofthe spray gun and a conduit 38 by which the coating material isdelivered to that passage. To heat the spray gun, a heating coil 40 inthe form of a sleeve is slipped over the barrel of the spray gun andheld in place by a nut 42.

The coating material in a liquid or semisolid state is contained in aclosed receptacle 44 (Fig. 8) which may be remote from the spray gun andmay be of any desired capacity, preferably such that an operator mayoperate the spray gun for an entire day without refllling thereceptacle. The coating material is conducted from the receptacle 44 tothe spray gun through the conduit 33 which is connected to the bottom ofthe receptacle. An air conduit 46 is connected to the top of thereceptacle and is connected to a source of air pressure, indicatedgenerally by the reference character 41, whereby air under pressure maybe delivered to the receptacle to force the coating material from thereceptacle through the conduit 38 to the .spray gun. The conduit 34through which air is delivered to the chamber 26 of the spray gun isconnected to the air conduit 46 by way of a valve 48 and a branchconduit 00. Thus, by manipulation of the valve 40, air may be permittedto enter the chamber 26 through the conduit 34 and passage 30, therebyopening the needle valve I8 and admitting the coating material to thenozzle. As soon as the valve 48 is closed, the air under pressure willbe out oif and the spring 28 in the cylinder 24 will close the needlevalve I8.

The heating coil 40 surrounding the barrel of the spray gun is connectedin an electric cir- The circuit consists of two variable resistances 62and 66 connected in series to an outside power line by a knife switch68. As illustrated, current from the knife switch 58 passes through acut-out 60, the

variable resistance 62, the variable resistance 66,

,and via the leads 54 and 66 to the coil 40. It

is to be observed that the second resistance 66 is connected across theterminals 68 of a pressure switch 64 and may be short-circuited by itwhen fluid under pressure is admitted to operate it.

In Fig. 3 the pressure switch 64 is shown in a' purely diagrammaticfashion, thereby to illustrate clearly the electric circuit. Thepressure switch 64 is of a commercial type and is shown indetail in Fig.4. The switch comprises a pair of dished disks I0 and I2 fastenedtogether face to face by screws 14 threaded through the peripheralportions thereof, and between the disks is clamped a flexible diaphragm16. The upper disk I2 is fastened by screws -'I8 to the base plate of abox 80 forming the body of the switch. A

aseaaas I00 projects upwardly from one side of the cup 00, and an arm H0is pivotally attached thereto at II2, the arm also being pivotallyattached at II4 to one of a pair of upstanding legs I00 fastened attheir lower ends to the base 80. Accordingly, upward movement of the cupcauses the arm III to tilt counterclockwise about the pivot II4. At oneend of the arm IIO there is formed a projection II6, to the end of whichis pivotally attached a rod III. A bar I20 is pivoted at I22 upon onewall of the box 80, one end of the bar having a depending leg I24 whichis adapted to rest upon the base of the box 00 and the other end ofwhich carries an upright I20 having a contact I28 thereon operable tobridge the terminals 68. The terminals 68 are mounted on a strut I3Iextending between and fastened to the opposite sides of the box 80. Thecontact I28 is snapped into and out of engagement with the terminals 66by a spring I32 which is fastened at one end to the rod H8 and at itsother end to the leg I24. As illustrated, when the arm H0 is caused totilt about the pivot H4 in a counterclockwise direction, the end of therod I I8 fastened to the projection I I6 is brought down below the pivotpoint I22, and the spring I32, which is now exerting an upward pull,causes the bar I20 to tilt in a clockwise direction about its pivot I22,thereby to snap the contact I20 into engagement with the terminals 68.Thus, the resistance 66 is short-circuited. When the air pressure is cutoff, the diaphragm I6 is collapsed, that is, returned to its lowermostposition by a spring 94. To this end, the sprin 94 is seated at one endin the cup 90 and is held under compression by an adjustable nut 86threaded on a screw 98, thereby urging the diaphragm downwardly. Theupper end of the screw is provided with a flanged head I00 whichprojects through an aperture I02 formed in a horizontal plate I04joining the upper ends of the upstanding legs I06. Clockwise movement ofthe arm IIO causes the rod II8 to rise above the pivot I22, as shown inFig. 4. The spring I32 thus exerts a downward pull and causes the barI20 to tilt in a counterclockwise direction to break engagement betweenthe contact and terminals, thereby to cause the current to pass throughthe resistances 62 and 66 in series. A strap I34 fastened to the base 80limits the upward movement of the rod H8. The clockwise conduit 82 isconnected at one end to the lower disk I0 and at its opposite end to thevalve 48. Thus, air under pressure may be delivered through the conduit82 to the underside of the the plate 06 by the aforesaid screw 02. Afinger movement of the arm H0 is limited by a screw I36 threaded throughthe end of the arm H0 and adjustably secured therein by a lock nut I38.

The conduit 82 leading to the pressure switch 64 is connected to themain air conduits 46 and 50 through the valve 48 so that when air isadmitted to the spray gun, air is also admitted to the pressure-operatedswitch 64 and, consequently, when the coating material is being forcedthrough the spray gun. the contacts of the pressure-operated switchremain closed. As a result, a maximum of current passes through theheating coil 40 because of the fact that the second resistance 66 isshunted or short-circuited out of the circuit. When the valve 48 isturned to a position to cut off the flow of air to the spray gun, air isalso cut-off from the pressureoperated switch so that the contacts areseparated, thus cutting the second resistance 66 back into the circuitin series with the resistance 62. As a result, a minimum of currentpasses through the circuit and the amount of heat generated at the spraygun is reduced. It is to be observed that both the resistances 62 and 60are variable terial to pass into the nozzle.

and by properly adjusting them the amount of current delivered to theheating coil iii of the spray gun while it is in operation and thecoating material is passing therethrough and the amount of currentdelivered to the heating coil 40 of the-spray gun when no coatingmaterial is passing therethrough can be so balanced that the temperatureof the spray gun will be uniform whether the gun is or is not inoperation.

In using the apparatus, the operator throws on the main switch 58 whichheats the coil 40 of the spray gun. When it is desirable to coat anarticle such as a shoe part, the operator directs the spray gun at theshoe part or holds the shoe part in front of the spray gun and turns thevalve 48 which admits air under pressure to the piston-operated needlevalve l8, thereby causing it to open and to permit the coating ma-Simultaneously, air is admitted to the underside oi the diaphragm 16,and the contact I28 and terminals 68 are closed, thereby toshort-circuitthe variable resistance 68, which increases the current inthe circuit so that the quantity of heat at the spray I gun increaseswith the flow oi the coating material through the spray gun. when thevalve 48 is manipulated to cut oil the air, the p stonoperated needlevalve II is closed by the spring 28. The diaphragm I8 is returned to itslowermost position by the spring II. and the contact I28 and terminals.88 are separated so that-the current again passes through bothresistances 82 and 88, thus reducing the current in the circuit andconsequently the amount oi! heat at the spray gun. By setting thevariable resistances beforehand, a balance may be established so thatthe temperature of the spray gun may be maintained substantiallyconstant. Thus the spray gun may be operated without overheating,whether it is used continuously or intermittently.

The method oi forcing an unheated spray material to a spray gun andthere heating it to liqueiy it forms no part of the present inventionbut forms the subject matter of application Serial No. 461.435. filledOctober 9, 1942, in the name of John J. E p y- Having described myinvention. what I claim as new and desire to secure by Letters Patentoi, the United States is:

1. Apparatus for ap lying a s ray coating to an object, said apparatusbeing used in connect on with a source oi fluid pressure and a source ofelectric power. said apparatus comprising a spray gun. a source orcoating material; means for normally closing the nozzle of the spra gun.electrical means for heating the spray gun. said electrical heatingmeansincluding a resistance and a switch operable to short circuit apart of the resistance when the nozzle is open. means whereby said fluidunder pressure effects delivery of the coating material from said sourceto said spray gun and simultaneously opens said firstnamed means andoperates said switch, and means for cutting oi! the flow oi fluid underpressure to said first-named. means and switch without aflectingdelivery or the chitin: material to the spraygun. l

2. Apparatus for applying a spray coating to an object, said apparatusbeing used in connection with a source of fluid pressure and a source ofelectric power, said apparatus comprising a spray gun, a source ofcoating material, means for normally closing the nozzle of the spraygun, electrical means for heating the spray gun, said electrical meansincluding an electric circuit connecting said heating means to a sourceof electric power, a resistance and a switch operable to short circuit apart of the resistance when the nozzle is open, means whereby said fluidun-' der pressure efle'cts delivery the coating material from saidsource to the spray gun and simultaneously opens said ilrst named meansand operates said switch and atomizes the coating materialas it isdischarged from the nozzle, and means for cutting off the flow of fluidunder pressure to said first-named means and switch without aflectingdeliver of the coating material to the spray gun.

3. Apparatus for applying a spray coating to an object, comprising aspray gun having materlal and air passages therein, a source 0! coatingmaterial, a conduit connecting said source as to the material passage ofthe gun, a valve'in said material passage for controlling the passage ofcoating material therethrough, a conduit connecting the air passage to asource of compressed air, means in said air passage to ac- 80 tuate saidvalve, heating means surrounding the spray gun, an electric circuitconnecting the heating means to a source of electric power, resistancemeans in the circuit, a pressure-operated switch to short-circuit a partof the resistance.

a conduit connecting. the pressure-operated switch to said source ofcompressed air, and a valve between said source of compressed air andsaid secondand third-named conduits operathe pressure-operated switch.

4. Apparatus for applying a spray coating to an'obiect, comprising aspray gun having ma-- terial and air passages therein, a container forcoating material, a conduit connecting said container to the materialpassage of the spray gun, a conduit connecting the container to a sourceof compressed air to force the coating material through the first-namedconduit to the material air passage to actuate said valve, heating meanssurrounding the spray gun, an electric circuit connecting the heatingmeans to a source 0! electric power, resistance means in the circuit,

a pnemnatically'opcratedswitch to short-circuitapartoftheresistanceaconduitconnectinl the pneumatically operated switchto the source of compressed air, and a valve between the source ofcompressed air and the'third and fourthnamed conduits operable to admitair simulta neously to the pneumatically operated menu and switch.

ble to admit compressed air simultaneously to the; means for actuatingsaid first-named valve and wnmu as. nooon'ron.

